1. Field of the Invention
The present invention relates to an improvement in busbar connection structure, and more specifically to busbars incorporated in a junction box used with electric appliances for an automotive vehicle. Here, busbars are metallic strip-shaped conductors connected between plural circuits so as to construct internal circuits. Through the busbars, a relatively large current is passed. That is, the busbars are used as common lines for connecting a negative (or positive) terminal of a dc power supply or each phase of an ac power supply to load circuits.
2. Description of the Prior Art
FIG. 1(A) shows an example of an internal circuit formed by three busbars 1A, 1B and 1C and two insulating plates 2A and 2B. As shown in FIG. 1(B), each busbar 1 is formed with a horizontally extending trunk portion 1e, plural horizontal branch portions 1f, 1g and 1h, plural upward extending tab-shaped male terminals 1a, and plural downward extending tab-shaped male terminals 1b.
With reference to FIG. 1(A) again, a first busbar 1A is arranged on a first insulating plate 2A by inserting a downward extending tab-shaped male terminal 1b into a hole 2a formed in the plate 2A. A second busbar 1B is sandwiched between the first insulating plate 2A and a second insulating plate 2B by inserting plural upward extending tab-shaped male terminals 1a into holes 2a formed in the first plate 2A and plural downward extending tab-shaped male terminals 1b into holes 2b formed in the second plate 2B. In the same way, a third busbar 1c is placed on the lower surface of the third insulating plate 2B by inserting plural upward extending tab-shaped male terminals 1a into holes 2b formed in the second plate 2B, respectively. The inserted tab-shaped male terminals of one busbar arranged on one surface of the insulating plate are connected to the inserted tab-shaped male terminals or the trunk or branch portions of the other busbar arranged on the opposite surface of the same insulating plate, respectively by soldering, for instance.
In the prior-art busbar connection structure, however, since two busbars arranged on both the opposite surfaces of a single insulating plate are connected by use of upward or downward extending tab-shaped male terminals, there exists a problem in that the busbar conductor arrangement density on an insulating plate is lowered and therefore the material yield (a ratio of useful material quantity to wasted material quantity) is lowered, thus increasing the material cost.